What makes this different from regular md? I'm not familiar with unRAID.
replies(2):
unRaid takes multiple partitions, dedicates one or two of them to parity, and hands the other partitions through. You can handle those normally, putting different file systems on different partitions in the same array and treating them as completely separate file systems that happen to be protected by the same parity drives
This enables you to easily mix drives of different sizes (as long as the parity drives are at least as large as the largest data partition), add, remove or upgrade drives with relative ease, and means that every read operation only goes to one drive, and writes to that drive plus the parity drives. Depending on how you organize your files you can have drives that are basically never on, while in an md array every drive is used for basically every read or write.
The disadvantages are that you lose out on the performance advantages of a RAID, and that the raid only really protects against losing entire disks. You can't easily repair single blocks the way a zfs RAID could. Also you have a number of file systems you have to balance (which unRaid helps you with, but I don't know how much of that is in this module)
The magic of ZFS repairs isn't in RAID itself, IMO, it's in being able to take your cold replicated dataset, e.g., from LTO, an external disk, remote server etc, and repair any issues without needing to resilver, stress the whole array, interrupt access, or hurt performance.
RAID can correct issues, yes, but ZFS as a filesystem can repair itself from redundant datasets. Likewise, you can mount the snapshots like Apple Time Machine and get back specific versions of individual files.
I wish HN didn't limit comment depth as these are great questions and this is heavily under-discussed, but it's arguably the best reason to run ZFS, IMO.
Another way of putting this—you don't need a RAID array, you can do individual ZFS disks and still replicate and repair them. There's no limits to how many replicas or mediums you use either. It's quite amazing for self-healing problems with your datasets.
I think it’s actually a flamewar detector that you may be hitting. In any case, next time try selecting the timestamp of the comment which you wish to reply to; this works when the reply button is missing and the comment isn’t [dead] or [flagged][dead] iirc.